Knife sharpening tool

ABSTRACT

A power driven tool for sharpening knives and similar cutting blades which is characterized by a driving motor arranged with its output shaft disposed vertically and carrying on its upper end a disc on the top face of which there is mounted a circular grinding plate or sheet, the motor being mounted on a supporting base member which in turn is mounted with a flexible connection on a suction cup for anchoring the tool on a supporting surface while permitting a limited amount of tilting from a normal upright position and having a degree of flexibility which insures return to the upright position when the tilting force is removed.

United States Patent Dewitt [4 Aug. 1,1972

[54] KNIFE SHARPENING TOOL [72] Edward J. Dewitt, 1311 Forest Glen Dr., Winnetka, 111. 60093 Filed: Feb. 22, 1971 Appl. No.: 117,540

Inventor:

US. Cl. ..51/109 BS, 51/166 TS, 51/209 R Int. Cl. ..B24b 3/54 Field of Search ..5 H109 R, 109 BS, 166 R, 166

51/166 PE, 209 R, 210; 24l/DIG. 17

References Cited UNITED STATES PATENTS Primary Examiner-Donald G. Kelly Attorney-Greist, Lockwood, Greenawalt & Dewey [5 7] ABSTRACT A power driven tool for sharpening knives and similar cutting blades which is characterized by a driving motor arranged with its output shaft disposed vertically and carrying on its upper end a disc on the top face of which there is mounted a circular grinding plate or sheet, the motor being mounted on a supporting base member which in turn is mounted with a flexible connection on a suction cup for anchoring the tool on a supporting surface while permitting a limited amount of tilting from a normal upright position and having a degree of flexibility which insures return to the upright position when the tilting force is removed.

7 Claims, 5 Drawing Figures PATENTEDAus' 1 m2 v sum 1 OF 2 INVENTOR EDWARD J. DEW/TT L BY 1 ATT'YS PATENTEDAUG I I972 I 3.680.264

SHEET 2 OF 2 INVENTOR EDWA RD 'J. oswvrr ATT' KNIFE SHARPENING TOOL This invention relates to tools and is more particularly concerned with improvements in a tool which is especially useful for sharpening or grinding knife blades and similar objects.

Many tools have been designed which are adapted for various uses including the grinding or sharpening of knife blades and similar articles or objects. Generally, the tools which have been most commonly offered for such purposes have taken the form of power driven grinding wheels or disc elements which have included a rigid mounting, with the grinding element being rotated in a generally vertical plane and at a relatively high constant speed so that the operator has a limited range of visibility and a high degree of care must be exercised to avoid applying a pressure which will result in the removal of more than the desired amount of metal and to avoid too lengthy contact of the work with the grinding element which will result in damage by overheating. It is a general object of the present invention, therefore, to provide a sharpening tool for knives or similar objects which enables the user to better control the manner in which the object is engaged with the grinding element, which is more convenient to use, which is less hazardous to the user and less likely to damage the work than the tools heretofore provided for this and similar purposes.

A more specific object of the invention is to provide a sharpening or grinding tool for cutting blades and similar objects which is of relatively simple construction, which is sturdy and requires a minimum of maintenance, which has a relatively long life, and which may be economically produced.

Another object of the invention is to provide a sharpening or grinding tool for knives and similar articles which affords a high degree of safety for the user, which enables the user to readily control the amount of metal removed by the operation of the tool and which requires little skill for successful operation.

A further object of the invention is to provide a grinding tool which is automatically responsive to the force or pressure applied by the user in contacting the grinding face of the tool with the work piece so as to reduce to a minimum the risk of injury to the user and/or the work piece.

These and other objects and advantages will be apparent from a consideration of the knife sharpening tool which is shown by way of illustration in the accompanying drawings wherein:

FIG. 1 is a perspective view of a knife sharpening tool which embodies therein the principal features of the invention, the view showing the manner in which a knife blade may be engaged with the grinding surface of the tool;

FIG. 2 is a side elevation of the tool of FIG. 1;

FIG. 3 is a vertical cross section with parts in elevaobserve the cutting operation and to exercise a high degree of control over the same in order to avoid injury to the operator in the use of the tool and to minimize the chances of damage to the work piece which could result due to an improper grinding angle, excessive pressure or other errors likely to be made by the operator when careful observation of the grinding action is difficult or impossible as in many tools heretofore provided for this purpose.

As shown in FIGS. 1 to 4, the tool comprises an electric drive motor 10 which is mounted on a base plate or support member 12, the latter being in the form of a short length of a solid cylinder, preferably of steel, or other metal, so as to afford a stable and normally rigid base. The base member 12 is in turn mounted on a suction cup device 14 for supporting the tool on a table, bench top, or other structure (not shown) which will afford a generally horizontal supporting surface. The motor 10 is arranged with its output or drive shaft 16 disposed vertically and carrying on its top end a cylindrical support plate or disc 18 which has a cylindrical grinding disc element 20 seated in a shallow circular recess 22 in the upper face of the support plate 18 with the top surface or face 24 of the disc 20 in a plane above the margin of the support member 18 where it is available for contact by a work piece which it is desired to sharpen, for example, the knife blade 26 which is illustrated in FIG. 1.

The motor 10 is a type which is commercially available such as, for example a 1/50 horse power split phase motor with a driving torque which will rotate the support plate 18 and grinding disc 20 at a suitable grinding speed for the disc 20 and which will decrease in speed or slow down upon the application of force or pressure exceeding a predetermined amount so as to give the user warning of power failure.

The motor 10 is rigidly connected to the base plate 12 by a pair of machine screws 28 as shown in FIG. 3 or other suitable fastening elements. The cylindrical base plate 12 is a relatively thick metal member of substantial weight so as to stabilize the device. It is connected on its bottom face to a neck forming base portion 30 of the suction cup 14 by bolt 32 or equivalent fastening means.

The suction cup 14 is formed of rubber-like material having a degree of resiliency so as to enable the neck portion 30 to flex under a vertical component of force which results from pressure applied to the top face 24 of the grinding element 20 which is effective at a point offset relative to the vertical axis and to return the grinding plate 20 to its normal position when the pressure is discontinued. The tilting effect which results due to the resiliency of the neck portion 30 of the suction cup 14 when downward pressure is applied to the grinding plate 20 is of limited extent, there being postlike stop members 34 upstanding in spaced relation around the margin or rim of the suction cup 14 which 1 help prevent tipping the device over and breaking the hold of the suction cup on the supporting surface when the device is in use. A control switch 36 may be mounted in the motor assembly.

. The plate or disc support 18 for the grinding element 20 is of rigid'material and is fastened by a set screw 38 or the like to the top end of the motor drive shaft 16. The recess-22 in the top face is relatively shallow. Its

depth depends upon the thickness of the grinding disc so as to enable the grinding disc 20 to seat in the recess, preferably, without the aid of any adhesive,

retaining the disc during rotation of the support I member 18 with the entire top grinding surface of the disc available, without obstruction, for contact by the edge of the blade. The grinding disc 18 may be, for example, any round abrasive disc product such as bonded resin or resin-rubber or sheet mix.

In using the illustrated tool for a grinding operation, such as the sharpening of a knife blade 26, the operator engages the knife edge on the top surface 24 of the rotating grinding disc 20, holding the blade at the proper angle relative to the face of the tool and applies pressure for a sufficient time, to remove the desired amount of metal, moving the blade 26 across the grinding surface as required for uniform sharpening of the edge. If too much pressure is applied the motor speed will decrease to the stalling point. This limits the amount of work the abrasive disc will do. In effect, the abrasive and the motor decide when they are in balance for effective grinding. There is nothing to interfere with moving the blade across the grinding surface. If the blade 26 is moved too far from the center of the grinding surface 24 and sufficient pressure applied, the plate 20 will tilt and the blade 26 will slide off the rim of the grinding surface. Since the grinding action may be readily observed by the operator, it is easy to judge the proper position and pressure to obtain the desired grinding action.

In a modified arrangement which is illustrated in FIG. 5, the support plate 40 is provided which has a planar top surface 42 for mounting thereon a paper or fabric backed grinding element 44. The grinding element 44, which is in the form of a disc having a suitable abrasive, may be secured on the surface 40 by any suitable adhesive, preferably a peelable type which will permit ready removal and replacement of the disc. Otherwise, the tool is the same as shown in FIG. 1 and operates in the same manner.

I claim:

1. A device for sharpening knife blades comprising a base forming plate member, a suction cup means for mounting the base forming plate member in a horizontal position, which suction cup means is connected to the underside of said base forming plate member by a portion thereof which provides a resilient support permitting tilting of said base forming member under vertical components of force when applied from above and outside the vertical axis, a drive motor mounted on said base forming plate member and having a drive shaft extending vertically, a disc-like support member mounted on said drive shaft for rotation when the motor is operated, said support member having means on its topmost surface for mounting a grinding disc whereby the grinding disc presents a top surface for unobstructeden'gagement by the knife blade, said support member being adapted to tilt when vertical pressure on the grinding disc is outside the vertical axis and exceeds a predetermined amount, the tilting action being resisted by the portion of the suction cup means connectin the suc ion cu and th base formin late m m e 5. A device for harpeni ng knife blad%as as set fbrt h in claim 1 wherein said motor has a driving torque which results in a decrease in speed when excessive vertical pressure is exerted on the top surface of the grinding disc.

3. A power driven tool for sharpening knives comprising a base forming member, a means for mounting the base forming member in a generally horizontal position which mounting means is connected to said base forming member so as to provide a resilient support permitting tilting of said base forming member under vertical components of force when applied from above and outside the vertical axis, a motor mounted on said base forming member and having a drive shaft extending vertically and a disc member mounted on said drive shaft for supporting on its topmost surface a relatively thin grinding disc, said grinding disc having on its top an abrasive surface for engagement by the knife whereby said motor and grinding disc will tilt when pressure is exerted on the disc at a point outside the vertical axis and in excess of a predetermined amount, the tilting action being resisted by the resilient support for said base forming member.

4. A power driven tool as set forth in claim 3 wherein said means for mounting the base forming member comprises a suction cup secured in depending relation on the bottom of said base forming member by a connecting member which is resilient.

5. A power driven tool as set forth in claim 3 wherein said means for mounting the base forming member comprises a bottom section adapted to be detachably secured to a support and a connecting section which is resilient so as to permit limited tilting of said motor upon the application of a vertical component of force on said grinding disc in an area offset laterally from the vertical axis of said grinding disc.

6. A power driven tool as set forth in claim 3 wherein said disc member has a top surface with a relatively shallow recess therein for detachably mounting said grinding disc with the abrasive surface thereof uppermost and unobstructed so as to be wholly available for grinding operations.

7. A power driven tool for sharpening knives comprising a drive motor disposed with its drive shaft upstanding in a generally vertical position, a means for mounting said motor which is connected to and depends from the lower side thereof so as to provide a resilient support permitting tilting of said vertical shaft under vertical components of force when applied from above and outside the axis of said shaft, and a disc member mounted on said drive shaft and providing on its top an abrasive surface for engagement by the knife whereby said motor and disc member will tilt when pressure is exerted on the member at a point outside the vertical axis of said shaft and in excess of a predetermined amount, the tilting action being resisted by said resilient support, and said motor and said abrasive surface being such that the motor speed automatically adjusts to proper balance with the abrasive surface for effective grinding.

NITED STATES PATENT OFFICE CER'HFKCATE 6F CQRREQTWN Patent No. 3,680,264 Dated August 1, 1972 Inventor(s) Edward J. Dewitt It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet, insert [73] Assignee Wallace Supplies Manufacturing Company, Chicago, IlL, a corp. of Illinois Signed and sealed this 19th day of December 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents USCOMM-DC 60376-P69 =ORM PO-105O (10-69) v: u.s. GOVERNMENT PRINTING omcz; won 0-3064. 

1. A device for sharpening knife blades comprising a base forming plate member, a suction cup means for mounting the base forming plate member in a horizontal position, which suction cup means is connected to the underside of said base forming plate member by a portion thereof which provides a resilient support permitting tilting of said base forming member under vertical components of force when applied from above and outside the vertical axis, a drive motor mounted on said base forming plate member and having a drive shaft extending vertically, a disc-like support member mounted on said drive shaft for rotation when the motor is operated, said support member having means on its topmost surface for mounting a grinding disc whereby the grinding disc presents a top surface for unobstructed engagement by the knife blade, said support member being adapted to tilt when vertical pressure on the grinding disc is outside the vertical axis and exceeds a predetermined amount, the tilting action being resisted by the portion of the suction cup means connecting the suction cup and the base forming plate member.
 2. A device for sharpening knife blades as set forth in claim 1 wherein said motor has a driving torque which results in a decrease in speed when excessive vertical pressure is exerted on the top surface of the grinding disc.
 3. A power driven tool for sharpening knives comprising a base forming member, a means for mounting the base forming member in a generally horizontal position which mounting means is connected to said base forming member so as to provide a resilient support permitting tilting of said base forming member under vertical components of force when applied from above and outside the vertical axis, a motor mounted on said base forming member and having a drive shaft extending vertically and a disc member mounted on said drive shaft for supporting on its topmost surface a relatively thin grinding disc, said grinding disc having on its top an abrasive surface for engaGement by the knife whereby said motor and grinding disc will tilt when pressure is exerted on the disc at a point outside the vertical axis and in excess of a predetermined amount, the tilting action being resisted by the resilient support for said base forming member.
 4. A power driven tool as set forth in claim 3 wherein said means for mounting the base forming member comprises a suction cup secured in depending relation on the bottom of said base forming member by a connecting member which is resilient.
 5. A power driven tool as set forth in claim 3 wherein said means for mounting the base forming member comprises a bottom section adapted to be detachably secured to a support and a connecting section which is resilient so as to permit limited tilting of said motor upon the application of a vertical component of force on said grinding disc in an area offset laterally from the vertical axis of said grinding disc.
 6. A power driven tool as set forth in claim 3 wherein said disc member has a top surface with a relatively shallow recess therein for detachably mounting said grinding disc with the abrasive surface thereof uppermost and unobstructed so as to be wholly available for grinding operations.
 7. A power driven tool for sharpening knives comprising a drive motor disposed with its drive shaft upstanding in a generally vertical position, a means for mounting said motor which is connected to and depends from the lower side thereof so as to provide a resilient support permitting tilting of said vertical shaft under vertical components of force when applied from above and outside the axis of said shaft, and a disc member mounted on said drive shaft and providing on its top an abrasive surface for engagement by the knife whereby said motor and disc member will tilt when pressure is exerted on the member at a point outside the vertical axis of said shaft and in excess of a predetermined amount, the tilting action being resisted by said resilient support, and said motor and said abrasive surface being such that the motor speed automatically adjusts to proper balance with the abrasive surface for effective grinding. 